1. Field of the Invention
This invention relates to an optical fiber impulse sensor fabrication method, which senses an impulse by converting the impulsive stress into an optical transmission characteristic of the optical fiber, and which enhances workability.
2. Description of the Related Art
As an optical fiber impulse sensor, there is a type in which a stress concentration sheet with square perforations is mounted in a straight portion of a U-folded or straightened heat-resistant plastic optical fiber (hereafter, referred to as HPOF), for example, and in which a rubber material is molded in constant width and thickness around the perimeter of those HPOF and stress concentration sheet.
A conventional optical fiber impulse sensor fabrication method is as follows: An iron round bar is placed along a stress concentration sheet in a rubber material to extrude the rubber material so that the rubber material covers the perimeter of the iron round bar and stress concentration sheet, and the rubber material is molded by means of a press to have a square cross section, and the iron round bar is pulled and removed from the cross section to form a cavity longitudinally extending through the inside of the rubber material, and the rubber material is then secondarily cross-linked to solidify it, and air is injected into the cavity from one longitudinal end, while an HPOF is inserted up to a predetermined position from the other end.
Refer also to JP-A-2005-140752.
In inserting the HPOF into the rubber material after removing the iron round bar, however, there is the problem of poor workability caused by the air injection into the cavity being complicated, and by the HPOF insertion into the cavity being time-consuming.